Telephone system



Novu 30 1926. 1,608,524

L.. F PORTER TELEPHONE SYSTEM Filed July 24, 1924 sheets-shed 1 Marginalwww@ Nov. 30 1926.

L. F. PORTER TELEPHONE SYSTEM Filed July 24,

1924 5 SheetsmSheai; 2

/n ven for e5/ie f Parier wfg Nov. 30 1926. 1,608,524

l.. F. Pow-rm TELEPHONE SYSTEM Filed July 24, 1924 3 Sheets-Sheet 5Patented No. 3o, 1926.

llUNITED STATES PATENT oFFlc'E.

Lnsnrn 1f. ronTnn, or Passaro, vNNW .mnsEYbas-srenon To WESTERN ELECTRICcorr- PANY, INconronaTnn, or NEW Yonx, N. Y., a coRronATIoN oF NEW Yonx.

TELEPHONE SYSTEM.

Application l'ed July 24, 1825. Serial No. 727,869. A

This invention relates to telephone systemsrand particularly to tollswitching systems wherein an operator establishes and supervisesconnections between. a: calling subscriber and a called subscriber atadistant point.

vThe object of the invention is to provide an improved circuitarrangement 'to take care of toll calls to and from machine U .switchingoli-lees, it being particularly an ob ject. to render the operation moreflexible through the use of certain common apparatus and to render theresults more certain through the extensionof the use of the suhperviscry signaling means.

A feature of this invention is a positional dialling arrangement whereindirect current is applied to one of the-talking Strands of the cord bythe operation of a master dialil ling key to cause an alternatingcurrent relay to be bridged across the talking strands ot a trunkleading to the distant endth'ere ot, and wherein alternating currentapplied to the talking strands of the cord through 2" a dial associatedwith the cord by the opera- Y tion ot vthe master dialling key isinterrupted by the dial to cause the bridged alternating current relayto translate the operation of the dial into impulses of any characterrequired toset switches associated with the distant end of the trunk.

Another feature of the invention Iis a positional or master ringingarrangement whereby ringing on a connected trunk is controlled by directcurrent over one of the talking strands ot' the cord circuits in use.

Another feature is a positional or master transfer arrangen'ient forswitching calls from one position to another on a toll switchboard.wherein selective operation of .signaling devices at the positions isattained' by varying the resistance in series with a battery supplied toone of the talking lll) strands ot the cord without making use ofv i5the sleeve or the other talking strand, the selective operation of thesignaling devices being attained. through the use of marginal relaysdirectly connected to such strands of [he trunk with which t-he cord isassociated.

A further feature of the invention is a 'sleeve supervisory arrangementwherein the bridgedsupervisory equipment is associated with t-he trunkinstead of the cord and the signals are transferred by this equipment tothe sleeve of thecord, this equipment beingcontrolled from the distantend of the trunk. An operators talking key individual to the cord will,when operated, transfer the sleeve circuitof the cord directly from asupervisory signal to a marginal relay arrangement which controls thesupervisory signal so that vthe supervisory signal will be properlycontrolled in either normal or operated'position of the key.

The invention is shown in three figures which. when placed end to .endin the order in which'they are numbered, will disclose means forcompleting a connection from a .calling subscriber to a calledsubscriber at a distant point. Fig. 1 discloses a toll switching trunk;Fig. 2, anoperators position; and Fig. 3, a .toll line leading .to adistant point.

It is believed that the invention will be more fully understood from thefollowing detailed description of the operation of the circuits. Let itbe assumed that the subscriber at station 100 lwishes to establish aconnection with another subscriber at a distant point.

Following out the usual practice the subscriber at station 100establishes a connection to a recording toll operator who makes a recordof the station calling and the station to be called whereupon thecalling sub- 85 scriber hangs up and awaits developments. Theinformation taken by the recording operator is` passed to a lineoperator whose equipment is illust-rated in Fig. 2. This operatorthereupon inserts plug 200 of one of her cord circuits into jack 101which forms a terminal of a train of automatic switches through whichthe subscriber at station 100 may be reached. A circuit is establishedfrom battery through signal 201, contact springs 203 and 204 of key 202,sleeve of plug 200, sleeve of jack 101, winding of relay 102 to ground.Relay 102 becomes energized in this circuit without result at thepresent time. rlhe operator then actuates 100 the right hand portion ofkey 202 and the left hand portion'of key 211. The operation of key 202results in the establishment of a circuit fromv ground, contact springs205 and 206 of key 202, winding of relayl 207 to battery and groundresulting in the energization of relay 207. The actuation ot the righthand ortion of* key 202 also results in the estab ishment of asubstitute'v i vtime without eect.

The actuation of the left-hand portion o dialing key 211 results in theestablishment of a circuit from grounded batte-ry, resistance 216,contacts 217aud 218 of key 211, contacts 219 and 220 of key 221, upperouter armature and front contact of relay 207, tip conductor of lplug200, tip of the jack 101, repeating coi winding 103, armature 104 andits back contact of relay 105, winding of relay 106 to ground.l Throughthe energization of relay 106, a circuit is established from the tip ofjack 101 through repeating coil winding 103, condenser 107, winding ofalternating current relay 108, inner lower armature and front contact ofrelay 106, repeating coil winding 109, to the ring of jack 101 andthence to the ring of plug 200, front contact and lower outer armatureof relay 207, contact springs 222 and 223 of key 221, contact springs224 and 225 of key 211, to a source ot alternating current. the otherconnection to this'sourceof A. C. being Aextended through the impulsesprings 226 of dial 228. condenser 227 to a point in the circuit leadingto repeating coil winding 103 so that alternating current relay 108 isnow in a circuit with the source of alternating current and it Ebecomesenergized. The energization of relay 108 results in the establishment ofa circuit from ground, armature and contact of .relay 108, resistancecoils 110, winding of relay 111 to battery and'ground. Relay 111 becomesenergized and bridges relay 112 across the trunk leading to the train oauto- I matic switches indicated at the right of reimpulses. Suchimpulses are in the form of v short interruptions of the alternatingcurrent circuit for the energization of relay 108 and upon each suchinterruption relay 108 causes the circuit` of relay 111 to beopened,which in turn opens the circuit of relay 112 and in this mannermomentarily removesmanner fully explained in the rStokely Patent1,474,008 hereinbefore mentioned.

Relay'112 is a polarized relay and will respond to this reversal ot'current, whereupon a circuit is established from ground, armature andfront contact ot' relay 112, winding of relay 105to battery and ground.Relay 105 becomes energized and locks in a circuit including 'its ownwinding, front contact und armature 11.3, armature and front contact ofrelay `102 to ground. The energization of relay 105 results in theopening of the circuit for the energization of relay 106 and this relaynowbecomes deenergized vand removes the bridge containing relay 112 fromacrossl the trunkl leading to the substation 100. The deenergization ofrelay 106 also results in the opening of' the circuit ot' alterna-tingcurrent Yrelay 108 so that this 1e lay now becomes deenergized causingin'turn the deenergization of relay 111. vThe battery connectionextending through armature 104 is now transferred through thecorrespondingfront contact of relay 105 to the winding of relay 114which relay, however, being marginal does not become energized whileresistance 216 is in series therewith. The trunk conductors leading tostation are now extended through the back contacts of relays 106 land114 and a circuit is established through repeating coil winding 115.winding of relay 116, front contact and ar- Amature 117 of. relay 105,repeating coil Winding 118 tothe other side of the trunk so that relay116 is new bridged across the lll) trunk and is energized by the currentflowing therein. The energization of relay 116 places a resistance 119in parallel with the winding of relay 102 and so reduces the reisistance of the circuit between the sleeve ot jack 101 and ground thatthe marginal relay 210 becomes energized. Upon the euer.A gization ofthis relay a circuit is established from ground through resistancev215.y Varmature and front contact ofrelay 210, contact springs 214 and213, signal 201 to battery and ground so that this signal becomes et'-fective to notify the operator that the line of substation 100 has beenseized.

The Operator now .restores the dialing 'key iso .from battery throu key202, sleeve of plug 233, sleeve of jack Lacanau.

211 to normal and havingestablishsda connection to substation 100proceeds, without signaling such station, to establish a connection to`the wanted line. l For this` Lpurpose she inserts the plug 233 1n theoutgoing jack 300, whereupon a circuit is established hvthe winding ofrelay 235, winding of re ay 236, contact springs 237 and 238 of theright hand portlon of 300, normal contacts of the outer,left handarmature of'relay 301, winding of relay 302 to ground. Relay 302 becomesenergized 1n this circuit and causes the energization of relay 303whereupon a circuit is established from battery through the alternatecontacts of the right hand armature of relay 303 and thence in parallelthrough the bus si als 304, 305 and 306 to ground so that t ese usysignals, each'associated with a jack connected to the toll line, areenergized to indicate that this toll line is busy.

The current flowing in the circuit including the windings of relays 235,236 and 302, besides being suiicient to energize relay 302 ashereinbefore described, causes the energization of relay 235, but relay236 being marginal does not become energized at th1s time. Relay 235closes a circuit for vthe energization of relay 240, which is withouteffect at the present time. Ihe connection is now in a stable conditionawaiting further action on the part of the operator.v

The operator now manipulates the ringing key 229so as to actuate theright-hand set of contact springs. This results in the establishment ofa circuit from battery, through the contacts 241 and 242 of key 229,contacts 243 and 244 of key 211, contacts 245 and 246 of key 221, innerup er armature and front contact of relay 207, tip of the plug 233, tipof jack 300, upper winding of impedance coil 318, winding of marginalrelay 307, resistance 308, to' ground. Current in this circuit issuilicient to energize marginal relay 307 since no resistance similar toresistance 216 is included in the circuit. Relay 307 in attracting. itsarmatures, connects a source of ringing current to the windings ofrepeating coil 309, whence by induction ringing current is transmittedto the distant end of the toll line and the operator at that point issummoned. The operator now restores her ringing key, and when theoperator at the distant end of the toll line answers, informationregarding the wanted line is passed and such wanted subscriber 1sconnected'to the toll line in the' usual wa f.

Let us first assume that the wanted subscribers line is connected to thetoll line immediately by the distant toll operator and that thisoperator has notified the originating operator whose equipment is shownin Fig. 2, that she is ringing. The originating operator thereuponactuates the left-hand terminating in plug 233.

portion of key 229 to summon the subscriber t l 100. This causesthesignal at station 100 to be actuated, and the subscriber at thatpoint will remove his receiver from the switchhook. l A

It should be noted that'with key 229 in normal position, the operatorstelephone set is connected to the toll line in the following manner:Tracing the circuit from the tip of plug 233, the connection extendsthrough the front contact and inner up er armature of relay 207,"Ycontacts 246 an 245 of key 221, contacts 244 and 243 of key 211,contacts 242 and 257 of key 229, contacts 249 and 258 of key 229,,armature and front contact of relay 240, windings 259 and 260 of theinduction coil forming part of the operators telephone set, condenser261, contacts 262 and 255 of key 229, contacts 254 and 253 of key 211,contacts 252 and 251 of lkey 221, inner lowerar'mature and front contactof relay 207, to the ring of plug 233. It will be noted that theoperators telephone receiver 263 is connected across the winding 260through the back contacts and inner armatures of relay 264, and that theopera tors telephone transmitter 265 is connected in. a circuit Which isinductiyely coupled with the windings 259 and 260.

In. a similar manner, with key 229 in its normal position, the operatorstelephone set is connected to the tip and ring conductors leadingthrough glug 200. Connection may be traced from t e ring of plug 200,front Contact and outer lower armature of relay 207, contact springs222and 223 of relay 221, contact springs 224 and 269 of key 211, contactsprings 270 and 271 yof key 229, condenser 261, transformer coils 260and 259, through the front contact and armature of relay 212, contactsprings 266 and'267 of key 229, contact springs 268 and 231 of key 229,contact springs 23LJ and 2180i key 211, contact springs 219 and 220 y ofkey 221, outer upper armature and front contact of relay 207 to the tipof plug 200,

It will thus be note-d that relay 212 controls the connection of theoperator-s telc phone set to that end of the cord circuit terminating inplug 200, and that relay 240 controls the connection of the operatorstelcphone set to that portion ci' the cord circuit If the operatorWishes to converse withthe subscriber at station to the exclusion of thedistant subscriber she will actuate the vthat thev connection betweenher telephone .and thus operate relay 310.

`set and plug 233 is broken but the connection with plug 200 isundisturbed. When `she actuates the left hand'contacts of key 221 theopposite effect is obtained.

The last operation described was the manipulation of the left-'handportion of key 229,\resulting in the operation of relay 114 and theringing of substation 100. Key 229 is then restored to its normalposition, and response of lthe subscriber at substation 100 is awaited.When the subscriber -at this sta? tion answers, the trunk extendingbetween the repeating coil windings 115 and 118 and substation 100 isrendered dry in the manner fully described in the Stokely Patent .i1,474,008 hereinbefore mentioned. Relay 116 -is'fthereupon deprived ofcurrent and 1t.re. stores its armature to normal whereupon theconnection through resistance 119 to ground is now traceable throughresistance 120 and the front contact and armature 121 of relay 105 tobattery. This connection results in a decrease of current flow through,marginal relay 210, so that such relay restores its armature to normaland causes the signal 201 lto become deenergized. lThis shows the. op-

erator that the subscriber at station 100 has answered and she may nowleave the 'connection by restoring key 202 to normal, whereupon theconversation between the-parties to the connection will take place. Y

At the termination of this conversation when the subscriber at station100 replaces his receiver'on the switchhook, relay 116 will becomeenergized and set up the condition heretofore described resulting in theenergization of marginal relay 210, so that signal 201 will beenergized.

The signal 234 associated with plug 233 is arranged in a similar mannerto the signal 201 associated with 'plug 200, but since the frelay 236has not become energized during this connection as hereinbeforedescribed, the signal 234 does not becomeener'gized. No switchhooksupervision over thetoll line is provided (in the present disclosure) sothat the operator has to-rely on signal201 for notification of the en'dof a conversation. It

will be noted, however, that when the key 202 is in normal position, aswhen the operator has the plug 233 in jack 300 and is busy tending tosome other connection, then `the supervisory signal 234 is in circuitwith the sleeve conductor and relay 302 and will be actuated -in themanner to be hereinafter described should the distant operator ring Shemay then Atake the plug 201 out of jack 101 and plug 233 out of jack300, and the connection will be restored to normal. The removal of plug200 from'jack 101 causes the deenergization of relay -102 andconsequently the deenergization'of relay 105, so that-the bridge acrossthe trunk vleading to substation 100 is removed and the train ofswitches allowed to return to normal. The removal of plug `233 from jack300 allowsthe deenergization of relay 302v and the conse uentdeenergi-zation of relay 303. Shortly ticreaftcr, busy signals 304 to306 will be deenergized, and the toll line apparatus will be placed inits normal condition.

In case the distant toll operator signals the outwardtolloerator, beforethe connection has been taA en down and while key 202 is in its normalposition, ringing current applied, at the distant end of the toll linewill operate relay 310 in an obvious circuit. Relay 310, in operatinreleases relay 312, which relay is norma y operated. Relay 312, inreleasing, connects ground at its contacts to operate rela, 301 in thefollowing vcircuitz'battery, win ing of relay 301, lefthandalternatecontacts of relay 303 and to ground at contacts of relay 312. Relay 301,1n operating, completes a circuit for relay 330 which relay operates inseries with interrupter 331, thereby alternately attracting andreleasing its armature. In practice, interrupter 331 operates relay 330about 120 times per-minute. Relay 301, when operated, transfers theholding circuit for relay 302, reviously completed over the sleeve ofthe )ack and plug to battery 280 through lamp 234, to battery in serieswith resistance 332 over the outer left alternate contacts ot relay 301.It should be noted that relay 302 is of such resistance that it does notpermit sufficient current to flow through the lilament of lamp 234 tocause its illumination, when these two devices are in series. Relay 301,in operating, also completes a substitute low resistance circuit forlamp 234 which can be traced from ground, through the winding of relay334, right-hand normal contacts ot' relay 330, inner left alternatecontacts ot' relay 301, inner left normal contacts of relay 315, outerleft normal contacts of relay 314, to the sleeve of the jack and thencethrough lamp 234 to battery and ground. Dueto the low resistance ofrelay 334, lamp 234 now lights. Relay 334, also operates 1n this circuitand supplies a substitute holding ground for relay 301 in place of theground supplied by relay 312, which ground will be removed as soon asthe ringing current ceases and relay 310 restores. When relay 330operates in step with interrupter 331 it opens the previously describedlow resistance circuit for ceA lamp 234, including. relay 334,"andsubstilay 330 operates instep with the interrupterf 335. Under theforegoing conditions, las relamp 234 ,will be alternately connected inseries with low resistance relay 334 and with the higher lresistanceunit 333, thereby causing it to iash as an indication to the oper# atorthat she is being signalled by the distant oiiice.

.When the operator manipulates key 202 to the right or talking position,lamp 234 and battery 280 are disconnected from the sleeve circuit ot'the cord and a high resistance circuit to battery including relays 236and 235, is substituted therefor. When relay 330 releases on an opensegment of interrupter 331, relay 334, which is now in series withrelays 236 and 235, releases due to the fact that it receivesinsuiicient current in this circuit to hold it operated. v

The release of relay 334 releases 301 which relay in turn opens thecircuit of relay l330.

We will now assume that the operator at the distant end of the toll lineof Fig. 3 is unable to establish a connection to the wanted partyimmediately and she therefore advises the operator of Fig. 2 of thiscondition, whereupon the operator of Fig. 2 will remove the plug 233from jack 300, allowing the toll line apparatus to restore to normal.

If it appears to the operator that the connection may not be securedwithin a reasonable time, she will also remove the plug 200 from thejack 101. Any later attempt to complete the call will be made in theusual manner hereinbefore described. Assuming now that the distant tolloperator desires a connection with station 100, she will ring on thetoll line in the usual manner. Alternating ringing current coming inover the toll line will be inductively transmitted through the repeatingcoil 309, through the armatures and back contacts of relay 307, thewindings of relayv 310 and condenser 311. Relay 310 momentarily attractsits armature and opens an obvious circuit for relay 312, whereupon thisrelay momentarily causes the establishment of a circuit from ground, thenormal contacts of relay 312, the left-hand armature and back contact ofrelay 303, the left-hand winding of relay 313, to battery. Relay 313attracts its armature and locks in a circuit from ground, its right-handwinding, its front contact and right-hand armature, the normal contactsand the right-hand armature of relay 303, to battery and ground. At thistime, relay 313 locks up under control of relay 303 and immediatelyplaces a busy condition on the toll line through a circuit establishedfrom battery, the lett hand armature and front contact of relay 313,through the windings of busy signals 304 to 306 in parallel, to ground.Through the right-hand armature of relay 313, a circuit is establishedfrom battery, the normal contacts and right-hand armature of relay 303,

the right-hand armature and front contact of relay 313, the right-handarmature and back contact of relay 314, the right-hand inner ar- Vmatureand back contact of relay 315 and signal 316, to ground. Signal 316 isassocil u i ated with jack 317 which is y.placed before e an inwardoperator. The cord circuits used by this inward operator, are the sameas those furnished at outward positions so that we will now assume thatthe operator having access to jack 317 will insert plug 233 into jack317 to answer the call incoming over the toll line. Upon the insertionof lug 233 in to jack 317 and the actuation of t 1e righthand set ofcontacts of key 202, a circuit will be established from battery inseries through the windings of relays 235 and 236, contacts 237 and23S-of key 202,'sleeve of plug 233, sleeve of jack 317, backcontact andouter left-hand armature of relay 314, back contact and inner left-handarmature of relay 315, normal contacts and the outer left-hand armatureof relay 301, winding of relay 302, to ground. Relays 302 and 235 becomeenergized in this circuit, but the marginal relay 236 does not respond.

Due to the energization of relay 235, relay 240 will become energizedand the oper ators telephone set will be connected to that end of thecord circuit leading through plug 233. Due to the energization of relay302, relay 303 will now become energized and open the circuit for theenergization of signal 316 so that this signal now is restored tonormal. A substitute circuit for the en ergization of busy signals 304to 306 is, however, established through the alternate contacts of theright-hand armature of relay 303. Relay 313 now being deprived ofcurrent through its locking winding, restores to normal. The inwardoperator now has .her telephone set connected to the toll line and mayconverse with the operator at the distant end and establish theconnection with station 100 over the trunk of Fig. 1 in the same manneras heretofore described. It an incoming call, as before describedrequires the attention of an outward or ticket writing operator, thatis, the operator who has access to jack 300, then the inward operatorupon receiving this information4 will manipulate her .transfer key 272to the right. A connection will thereupon be established from groundedbattery, contact springs 273 and 274, contact springs 262 and 255 of key229, Contact springs 254 and 253 of key 211, contact springs 252 and 251of key 221, inner lower armature and front vlcontact of relay 207, ringof the plug 233,

ring of jack 317, lower winding of impedance coil 318, left hand windingof relay 315, left-hand winding of relay 314, to ground. Relay 315 is anormal relay but relay 314 is marginal. However, since the connectiondescribed is from a source of lll" ` battery without a resistance 275therein,

f time.

both` these relays will become energized. Upon the attraction-of itsarmatures, relay 315 establishes a circuit from ground, the

front contact and outer left-hand armature of relay 315, the left-handwinding of relay 313, to battery and ground. At 'the same time, relay315 opens at its back contact and ,inner left-hand amature thehereinbeforev circuit also extends battery current through theright-hand armature and front Contact of relay 314, the right-handwinding of relay 314, signal 319, to ground. Signal 319 is associatedwith the Jack 300 before the outward operator. The operation of relays314 and 315 opens the sleeve circuit through jack 317, andV causesl thedeenero'ization of relay 235 and the relay 240, so that the operator isdisconnected from the cord circuit terminating in plug 233. Shetherefore restores key 202 to normal and takes the plug 233 out of jack317. This leaves the connection in the following condition: The relays302 and 303 are in normal condition and relays 313 and 314 are bothlocked under .control of the normal contacts of the right-hand armaturesof relay 303. Through the energization of relays 313 and 314, signal319`is actuated and will remain in this condition 'until the outwardoperator.

responds, and th busy si nals 304 to 306 are operated under contro ofrelay 313.

It may be well to explain at this timethat if the incoming call requirethe serv.-l

the energization of signal 320, which is asso-.

ciated with the jack 321, before athrough operator. In this case, itwill be noted that resistance 275 is included in the circuit through thelet-han`d windings of relays 315 and 314, and. hence relay 314 beingmarginal, does not become energized at this Therefore, when relay 313becomes energized, a circuit will be established from battery throughthe normal contacts and the right-hand armature of relay 303, therighthand armature .and front contact of relay 313, the right-handarmature and back contact of relay 314, the inner right-hand armatureand front contact of relay 315, through the right-hand winding ofrelay'315, signal 320, to ground.

' When plug 233 is inserted into either jack 300 or 321, relay 302 willbe reenergized 'as .ing current relay to said trunk.

'.gized, then the operator has' her set connected to both the plugs 200and 233 and may monitor onthe connection.

What is claimed is:

1, a telephone system, an operators position, cord circuits thereat, atrunk cir- 'cuit accessible to said cord circuits terminating 1n anautomatic switch, an alternating current relay individual to said trunkcircuit v'for controlling said switch, an operators dial common to' saidcord circuits for controlling said` alternating current relaya dialingkey common to said cord circuits, a relay individual to said trunk, saidrelay being responsive to 'said key and having means to operativelyconnect said alternat circuit of relays 313 and 314 2. In a telephonesystem, an operatorsI position, cord circuits thereat, a trunk circuitaccessible to said cord circuits terminating in an automatic switch, analternating current relay individual to said trunk circuit for.controlling said switch, means responsive to4 direct current connectedover a single conductor of a cord circuit and a corresponding conductorof said trunk circuit for bridging said alternating current relay acrossthe talking conductors of said trunk circuit,l a source of alternatingvcurrent for energizing said alternating current relay, and a dial forinterrulpting the flow of alternating current throng said relay.

3. In a tele hone system,`an operators position, cord circuits ther-eat,a trunk circuit accessible to said cord circuits terminating in anautomatic switch, an alternating current relay individual to said trunkcircuit for controlling said switch, means responsive to direct currentfor rendering said alternating current relayv operative, a source ofalternating current for energizing. said alternating current relay, anoperators dial. a dialing key at said position for associating said dialwith a particular one of said cord circuits, said dialing key whenoperated com-. pleting a direct current pathl over a single conductor ofa cord circuit and a corresponding single conductor of said trunkcircuit to operate said means, and an alternating cur rent -pathincluding said source of current. said dial, the talking conductors ofsaid cord circuit, the talking conductors of said trunk sition, cordcircuits thereat, trunk circuits accessible to said cord circuits, amarginal ielay individual to each of said trunk circuits connected to atalking conductor of ifs associated trunk, a key at each of saidpositions common to the cord circuits thereat, means individual to eachof said cord circuits :tor splitting the talking circuit thereof, asource oi" tone, Asaid key o erating to complete a circuit for said trunmarginal relay at one end of a cord circuit and operating to connectsaid source of tone to the other end of said cord circuit when said keyis operated in one Way, and to establish corresponding connections inthe opposite direction When said key is operated in another Wa 53.7 In atelephone system, an operators position, cord circuits thereat, trunkcircuits accessible to said cord circuits, a marginal and a non-marginalrelay individual to said trunk circuit, a master ringing key common tosaid cord circuits at said operators position, a master dialing keycommon to said cord circuits at said operators position, a keyindividual to each said cord circuit for connecting said common keythereto, said ke s operating to establish direct current pat is to saidrelays over said cord circuit, said dialing key including a resistancein such path whereby said relays are selectively operated by said keys.

6. In a telephone system, an operators position, cord circuits thereat,each of said cord circuits having la sleeve conductor, a supervisorysignaL/a trunk circuit accessible to said cord circuits, said trunkcircuit having a pair of talking conductors and a sleeve conductor,supervisory means for controlling said sleeve circuit`comprising adirect current relay bridged across the talking conductors of said trunkleading"to the distant f end thereof and a relay controlled over thesaid sleeve conductor, an operators listening key individual to eachcord circuit, said key when operated acting to transfer the cord ysleevecircuit from said supervisory signal to a pair of relays, one of saidrelays being responsive to the control exercised by said supervisorymeans and acting through said key to control said supervisory signalwhereby said supervisory signal is under control of said supervisorymeans in either normal or operated position of said listening key.

7. In a telephone system, an operators position, cord circuits tliereateach having a sleeve conductor, a supervisory signal in each sleeveconductor, a telephone line accessible to said cord circuits, said linehaving a pair of talking conductors and a sleeve conductor, analternating current relay in bridge of said talking conductors at saidposition and responsive to ringing current incoming over said line, andmeans controlled by said alternutn/g current relay for intermittentlyoperatiir said supervisory signal 1n a circuitinclu ing the sleeveconductor of said telephone line.

8: In a telephone system, 'an operators position, a cord circuitthereat, a sleeve conductor associated with said cord circuit, asupervisory signal in said .cord sleeve conductor, a ring-down toll lineterminating at said position and accessible to saidcord cirenit, saidtoll line comprising a pair of talking conductors and a sleeveconductor, an alternating current relay at said position connected inbridge to said talking conductors of said line and responsive tovringing current incomin thereover, and means controlled by said aternating current relay and included in said sleeve conductor of saidtoll line for intermittently increasing and Adecreasing the resistanceof said supervisory signal circuit.

9. In a telephone system, an operators position including a coi'dcircuit having "'a sleeve conductor, a telephone line terminating atsaid position including a pair of talking conductors and a sleeveconductor, a supervisory signal in said cord sleeve conductor andenergized over said line sleeve conductor when saidl cord is connectedto said line, an alternating current relay connected in bridge of saidline talking conductors and operated in response to ringing currentincoming over said line, and means associated with said line initiallycontrolled by the actuation of said alternating currentn relay toalternately increase and decrease the current in said supervisory signalenergizing circuit.

10. In a telephone system, an oprators position including a cord circuithaving a sleeve conductor, a telephone line terminating at saidpositionincluding a pair of talking conductors and a sleeve conductor, asupervisory signal in said cord sleeve con..

ductor and energized over said line sleeve conductor when said cord isconnected with said line, and means associated with said line responsiveto ringing current incoming thereover for flashing nal.

11. `In a telephone system, an operators position, a cord circuitthereat, a plurality of telephone lines terminating atsaid position andaccessible to said cord circuit, a supervisory signal for said cordcircuit energized when said cord is connected with oneof said saidvsupervisory siglines, and means responsive to ringing curf rent incomingthereover when said cord circuit is connected with one of said lines fordashing said supervisory signal.

12. In a telephone system, an operators position, cord circuits thereat,trunk circuits accessible to said cord circuits, a relay individual toeach of said trunk circuits connected to a talking conductor of itsassociated trunk, a marginal relay individual to each of said trunkcircuits connected to said talking conductor, a. plurality of keys atsaid position common to said cord circuits, one of said keys havingmeans for establishing a 5 circuit for energizing either of said relays,

another of said keys having means for establishing a circuit forenergizing only said first relay, and means under control of saidmarginal relay -for connecting alternating current to said trunk.

In Witness whereof, I hereunto subscribe my name this 22nd day of July,A. D. 1924.

LEsL'IE E. PORTER.

